title: Derivative couplings and analytic gradients for diabatic states, with an implementation for Boys-localized configuration-interaction singles.
abstract: We demonstrate that Boys-localized diabatic states do indeed exhibit small derivative couplings, as is required of quasidiabatic states. In doing so, we present a general formalism for calculating derivative couplings and analytic gradients for diabatic states. We then develop additional equations specific to the case of Boys-localized configuration-interaction singles (CIS)--in particular, the analytic gradient of the CIS dipole matrix--and we validate our implementation against finite-difference results. In a forthcoming paper, we will publish additional algorithmic and computational details and apply our method to the Closs energy-transfer systems as a further test of the validity of Boys-localized diabatic states.
authors.affiliation: Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Shervin
authors.initials: S
authors.lastname: Fatehi
authors.forename: Ethan
authors.initials: E
authors.lastname: Alguire
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Subotnik